It would be helpful to see what the tool's logs say. They are located in the installation folder (by default C:\Program Files (x86)\Netwrix\Disk Space Monitor\Tracing). Please post the logs and we'll see what's going on.

Also, "notify in real time" is an option that schedules the disk space monitor task to run every 10 mins. You may want to take a look at the history of the task to see if it simply fails to start.